Hydraulic drive for machine tools



Dec. 12, 1939.

F. WEGERDT HYDRAULIQDRIVE FOR MACHINE TOLS Filed Feb.' 26 195e Dec. l2, 1939. WEGERDT 2,182,908

I YDRAULIC DRIVE FOR-MACHINI TOOLS Filed Feb. 26, 1956 '7 Sheets-Sheet 2 Aorneys Dec. l2, 1939. F WEGERDT 2,182,908

HYDRAULIC DRIVE FOR MAC-HINE TOOLS File Feb. 2e, 1956 7 sheets-sheet 4 l l l l l l l 1 l /nvenon- FrL'Z Wege/"df De. 12, 1939. F. WEGERDT 2,182,908

HYDRAULIC DRIVE FOR MACHINE TOOLS Filed Feb. 26, 1956 7 Sheets-Sheet 5 Dec. l2, 1939.

F. WEGERDT HYDRAULIC DRIVE FOR MACHINE TOOLS Filed Feb. 26, 1936 '7 Sheets-Sheet 6 Dec. l2, 1939. F. WEGERDT 2,182,908

HYDRAULIC DRIVE FOR MACHINE TOOLS Filed Feb. 26, 1936 7 Sheets-Sheet '7 Patented Dec. 12, 1939 HYDRAULIC DRIVE FOR MACHINE TOOLS Fritz Wegerdt, Chemnitz, Germany, assignor to Friedrich Klapp, Solingen-Wald-Khld., Ger- Application February 26, 1936, Serial No. 65,896

\ In Germany March 2, 1935 7 Claims. (Ul. 121-45)` This invention relates to a hydraulic system for machine tools.

In machine tools with a reciprocating tool or element, the reversal of the oil flow could not heretofore be effected in a satisfactory manner,

particularly in machines effecting short strokes at high speed. To overcome the dead point action during the reversal, the heretofore known systems have usually employed either auxiliary control valves and an auxiliary pump, or mechanically operating snap-action mechanisms. Both these means are very complicated and require a large number of parts which are subject to wear and operate satisfactorily only when they are constructed with great accuracy. At high pressures and strains the use of snap-action mechanisms is excluded asi they are not capable of overcoming the dead point action satisfactorily under all conditions.

Auxiliary control valves have the further disadvantage that they do not permit as short strokes as desired of the reciprocatory machine element, particularly at high speed, for the reason that the time required to ll and rel-empty the passages and chambers on reversal of the main valve is relatively considerable. Further disadvantages of auxiliary control mechanisms are caused by the length time required to reverse the main valve and the machine, which time remains constant independently of the working speed of the machine. Thus the greater the working speed of the machine, the greater is the path traversed by its reciprocatory element before its reversal becomes effective, even after the auxiliary valve has been operated by means of a stop on said element in order to initiate the reversal of the main valve. cut in known systems with auxiliary valves, it will thus be seen that the reversal point of the planing machine is shifted, so that however the stops may be arranged, the shaping action of the machine is unsatisfactory.

The object of the present invention is to provide a hydraulic control for planing and shaping machines and the like by means of which the above mentioned disadvantages can be overcome by simple means, enabling the reciprocatory element of the machine -to be controlled rapidly, with precision, and reliably.

According to the present invention the system -comprises a conduit extending from one end of the working cylinder to a tank or reservoir for the pressure medium, and which conduit is also connected with one end of the main slide valve, said conduit having disposed therein an auxiliary On changing the speed of y valve which is operated by the reciprocatory machine tool or table. To reverse the power piston in one of .its dead point PQSitions, the auxiliary valve closes the out-flow from one end of the power cylinder and thereby causes the main valve 5 to be moved4 by entrapped medium against the .action of a spring in such a manner that this end of the power cylinder is connected to the pressure supply, and its other end to discharge into a tank. 0n reversal at the other dead point 10 position' the main valve is moved under the action of the spring, after the auxiliary valve has connectedthe heretofore pressure side of the power cylinder, to the tank. To prevent chattering of the main valve and to reliably hold it in its end l5 position after completion of this movement, without having to use an excessively strong spring, the main valve, the shifting of which controls the end of the power cylinder not connected with the auxiliary valvehas two piston heads of. diierent diameter enclosing an annular chamber, and the pressure differential acting on these heads due to the pressure medium in said chamber acts in the same direction as the force of the spring.

When the auxiliary valve, on reversal solely by the pressure of the entrapped pressure medium, has to move longitudinally, it might be under some `conditions that no pressure medium can ow away from the end of the cylinder not previously underpressure. Such condition might arise, for example, if the-tool or reciprocatory element has encountered a fixed stop so that no further movement takes place. According to the invention, this disadvantage is overcome by the arrangement that the operating chamber of the auxiliary valve wherein entrapped pressure medium acts upon a piston head of this valve to produce reversal thereof, is put indirect communication with the delivery side of the pump as soon as this chamber is closed against outflow. 4

A further feature of the invention consists in providing near those edges of the mainl valve which control the supply of the pressure medium to the return stroke end of the power cylinder, a

further piston head of. similar diameter forming means of a spring. In this manner the power stroke end of the power cylinder is relieved of pressure and its return stroke end placed under pressure, at the same instant, without the power piston being capable of making a further movement due to pressure medium flowing from the unloaded end of the cylinder to the auxiliary valve. The particularly important reversal from power stroke to return stroke thus takes place always at the same point independently of the speed of. movement.

To assist the operation of the spring at the reversal from power stroke to return stroke of the power piston, and to prevent chattering of the auxiliary valve, without allowing pressure medium to discharge from the closed discharge conduit of the return stroke side, and thus produce an undesired movement of the working piston, a piston head of the main valve is directly acted upon by the pressure medium in the same direction as the action of the spring, as soon as the discharge is opened from the power stroke end of the power cylinder.

Other improvements and arrangements according to the invention are shown in the accompanying drawings as hereinafter described.

The accompanying drawings show two constructional examples according to the invention, in simplified form.

Figure 1 is a longitudinal section through the control device according to the rst example and a diagrammatic longitudinal section through the working cylinder, the parts being in positions corresponding to movement of the working piston in the direction of the arrow.

Fig. 2 is a cross section through the control device taken on line 2-2 of Fig. 1.

Fig. 3 is a part section through the control device taken on line 3--3 of Fig. l

Fig. 4 is a part section through the control device taken on line 4-4 of. Fig. 1.

Fig. 5 is a cross sectional view of the control device takenon line 5-5 of Fig. 1.

Fig. 6 is a view corresponding to Flg. 1 with the parts in position corresponding to movement of the working piston in the direction contrary to the arrow, Fig. 1.

Fig. 7 is a similar view but with the parts in a further position wherein the pump is in direct communication with the tank and no force acts on the working piston.

Fig. 8 is a longitudinal section through the system according to the second example, with the parts in position for movement of the working piston in the direction of the arrow.

Fig. 9 is a partial section on the line XI-XI of Fig. 8.

Fig. 10 is asection on the line X-X of Fig. 8.

Fig. 11 is a section on the line XI-XI of Fig. 8.

Fig. 12 is a section on the line XII--XII of Fig. 8.

Figs. 13, 14 and 15 are views similar to Fig. 8, the parts being in positions for piston movement.

Fig. 16 is a diagrammatic View of a oat sheet showing the arrangement of the various valves.

The control device shown in Figs. 1-7 consists essentially of the three slide valves I0, 3 and 6 of which the middle valve 3 serves for engaging and disengaging the machine and is not operated during normal drive. The three valves are arranged in a housing |00, one face ||2 of which is conveniently directly mounted on the pump not shown in order to shorten the passages between the latter and the control device. The

housing I 00 is provided with three adjacent bores 5, 2 and 9 in which are inserted guide sleeves |0|-|08, |02 and |03. While the bores of the two sleeves |02 and |03 have the same diameter over their whole length, the bore for the sleeve |08 has a smaller diameter than that of the sleeve |0| so that these two sleeves form a step or shoulder in the bore 5.

Near the middle of the bore 2 there is located a conduit I leading to the delivery side of the pump. At about the same radial plane this bore is connected by a port 4 with an annular channel |04 in the sleeve 24, which is connected through slots |05 with the bore 5.

The sleeve |02 is also provided with an annular channel |01 communicating through slots |06 with the bore 2. The bore 5 is connected by a passage I8 provided in the sleeve |08 and in the control housing |00 to the annular channel |01. 'I'his channel |01 also communicates through a port |45 and a boring |46, in a manner not shown, with the discharge tank.

Between the annular channel |04 and the slots |05 in the sleeve |0|, and the passage I8 in the sleeve |08, a further annular channel |09 is provided in the sleeve |0|, which channel communicates with the bore 5 through slots |I0. To the annular channel |09 there is connected a conduit formed in the housing |00 and terminated in a connection face ||3 to which is attached a pipe ||5 indicated in dotted lines in the drawings.

While the annular channel |09 with the slots I| 0 is located on the one side of the annular channel |04, a further annular channel I|6 is provided in the sleeve |0| on the other side of the channel |04 which channel IIE is connected through slots ||1 with the bore 5.

In the sleeve |03 of the bore 9 there is provided an annular channel IIB connected by slots |49 with the bore 9. This channel IIB is connected with the annular channel IIS of the sleeve |0| through a conduit 8 in the housing |00; it is convenient to arrange the channel II8 with the slots |49, and the channel ||6 with the slots II 1, in approximately the same radial plane. Adjacent the annular channel I I8 there is provided in the sleeve |03 a further annular channel IIS also connected by slots I2 to the bore 9.' On the outside of the housing I 00 there is arranged a connection face |23, connected through a passage |2| with the annular channel ||9 and also connected to a. pipe |23 designated by a chain dotted line, leading to the oil reservoir or tank, not shown.

In the conduit 8 there terminates as shown in Fig. 5 a pipe 20 the further course of which is indicatedV in Figs. l, 6 and 7 by a chain dotted line. Through this pipe 20, and the pipe ||5 coming from the annular channel |09, the power cylinder |24 of the machine is operated. In this cylinder a piston |25 is longitudinally movably connected in known manner by a piston rod |26 to the machine tool element |21, for example the ram of a shaping machine, or the work table of a planing machine. Usually, as shown, the piston rod extends through the cylinder at one end only, so'that the two working chambers 1 and 98 which are fully separated from each other by the piston, have diierent cross sectional areas. The chamber 1 of the greater cross section is then used for the working stroke of the machine and ythe chamber 90 of smaller cross section is operative during the return stroke. For this reason in the following description the cylinder end 1 is referred to as the worldng end, and the cylinder end 99 as .the return end.

In the example illustrated the pipe I|5 is connected with the return end 99 and the pipe 20 is connected with the working end 1. The connections, however, may be reversed without depart- -ing from the invention. On the control valve 3, which is slidable longitudinally and rotatable in the sleeve |02 of the middle bore 2, are provided two piston heads |28 and |29 forming between them an annular space |44. A spring |30 abutting at one end against a cover I3I and at the other against the head |29, constantly urges-the valve 3 to its extreme left hand position in which a pin |32 on this piston head bears agaisnt a stuiling box |33 xed in any suitable manner to a cover |34 attached to the housing |00. The stufllng box |33 serves a bearing for the stem of the valve 3 which extends through said box I and is connected to a device, not shown, by means of vwhich the valve can be operated to a small extent. The end of the box |33 facing the piston head |28 has a notch |41 and a tapering surface In the sleeves I| .and |08 of the bore 5 there is arranged a longitudinal slidable main valve 6 by means of which the piston |25 of the working cylinder |24 is actuated.

The main valve 6 has two pistons I6 and I1 of which the piston head I1 is of smaller diameter and slides in the sleeve |08, while the piston head I6 of larger diameter slides in the vsleeve IOI. The slots through which the annular channel |04 is connected with the bore of the sleeve I0| have, as shown at inclined surfaces in the contact surface of the sleeve, the slots |05 including these inclined surfaces being wider than piston I6. On -the exterior end of the rod |35 of the valve 6 there is provided a helical spring I5 having one end abutting against the left end of the head I1 and the other end against a collar |36 which is slidably arranged on the rod |35 and bears against a part |31 fixed in any suitable manner to the housing |00. The valve 6 is held in' its extreme right hand position by means of a rod shaped extension |38 on the piston head I6, which rodfbears against the cover |3I which"` closes the right hand end both of the bore 5 and of the bore 2.- The annular space between the heads I6 and I1 is designated |39 and the space between the head I6 and the cover |39 is designated |40.

In the sleeve |03 of the bore 9 the slide valve I0 is longitudinally movable and as this valve assists to control the movement of the main valve 6, it is designated as an auxiliary valve. It consists essentially of a long piston head I4| and a shorter piston head |42 connected thereto between which an annular space I I is formed.' The shorter pisn ton head |42 has two annular grooves |3 and I4 at a certain distance apart, for cooperating with a ball I9 pressed by a spring |43. y

The apparatus operates in the following manner. During normal operation shownin Figs. 1

; and 6, the valve 3 is held by the spring |30 in the position illustrated. InFig. 1 the two valves 6 and I0 are shown in the position in which the return end 99 of the working cylinder |24 receives the pressure medium delivered by the pump. The

p pump delivers through the channel I, the annular space |44 between the piston heads |28 and |29 of the valve 3, the port 4, the annular channel |04 and the slots |05, into the annular channel |39 between the piston heads I6 and I1 of the main g valve 6. From there the pressure medium nows through the slots IIO, the annular channel |09, the passage I II4 and the pipe II5 to the return side 99 of the working cylinder |24 whereby the l piston |25 is moved to the right, Fig. 1, as shown by the arrow. The pressure medium expelled 5 from the working end 1 ows through the pipe 20, a part of the conduit 8, see Fig. 5, the annular channel I I8 and slots |49, into the annular chamber II of the auxiliary valve I0. From there it ows through the slots I2 into the annular chan- 10 nel II9, and thence through the bore |2I to the pipe |23 and the discharge tank.

Meanwhile the working end 1 ofthe power cylinder is connected through the pipe 20, the con- Iduit a, the annular channe1 ne and the slots In, l5 see Fig. 6, with the space Iat the right of the piston head I6 of the main valve 6. Since the piston head I6 is larger than the piston head II the valve 6 is forced to the right hand position shown, in a steady and reliable manner due to zo the force corresponding to the surplus annular area. This can be assisted hy means of the spring I 5 which is provided with a certain initial tension operative in this position.

The moving of the piston |25 from the right u hand end 1 of the-cylinder takes place as follows. The auxiliary valve I0 is moved, atthe end positions of the tool or of the work table, by means of the usual stops, or dogs, shown for instance in applicants co-pending application Serial No. so*

159,952, flied August 19, 1937, on the tool or work table, acting through suitable transmission means. These stops should be adjustable in order that the length and the position of the working stroke of the machine can be varied. When the working .as piston |25 located in the right hand end position is to be shifted the auxiliary valve I 0 is moved to the right so that the spring ball I9 engages the annular groove I3 of the piston headv |42. The piston head |4I of the auxiliary valve I0 in this 40 position covers.the slots` |49 of the sleeve |03, so that the annular channel II8 and therefore the conduit 8 no longer communicate with the annular space II of the auxiliary valve I0. The discharge from the working end 1 of the power cyl- 45 inder is consequently no longer connected to the discharge tank.v Since at this instant there is no discharge effective for the working end 1 of the power cylinder, the liquid in this end is under pressure since as hereinbefore described the de- 00 livery side of the pump is connected with the return end 99 of the power cylinder |24 and hence the left hand face of the power piston |25 is under the delivery pressure of the working medium. The increasing pressure thus produced in the working end 1 is transmitted through the pipe 20, the conduit 8, the annular channel |I6 and the slots |I1 to the space |40 at the right of` the piston head I6 of the main valve 6. Under the influence of this pressure the control valve 6 is 60` pushed to the left against the action of the spring I5, because the pressure entrapped in the space |40 acts on the total area of the piston head I 6 whereas the pressure liquid in the space |39 which is directly connected with the delivery side of the pump' operates on the annular area of the control valve 6 and the area of the piston head I6 is greater than that of the Apiston head I 1.

To the extent that pressure medium is transferred from theworking end 1 of the cylinder 70 into the space |40 and consequently thrusts control valve 6 to the'left, the working piston |25 wil advance a small amount to the right.

As soon as in this manner the right hand edge of the piston head I6 has moved beyond the right I5 hand edge of the oblique' surface 20 of the slots |05 thev delivery side of the pump is connected through the passage the annular chamber |44, and the port 4, to both the space |39 and the space |40 of the main valve cylinder. Meanwhile the valve 8 continues to move to the left because the area of the piston head I8 is greater than that of the piston head 1. At the instant, or shortly after, that the piston head I6 covers the left hand oblique surface and thus shuts off the annular space |39 from the slots |05, the right hand edge of the piston head |1 uncovers the connection between the port I8 and the annular space |39. 'I'he return end 99 of the power cylinder |24 is then connected through the pipe ||5 and the passage I, the annular channel |09,

' the slots ||0, the space |39, the port |8, the annular channel |01 and the passages |45 and |48, with the discharge tank. The pressure of the pump now acting upon the whole area of the piston head I8 of the valve 6, first presses the valve as shown in Fig. 6 against the action of the spring I5 into its left hand position and subsequently begins to shift the power piston |25 to the left in the direction opposite to its previous movement. Meanwhile the liquid pump, delivers through the inlet passage the annular space |44, the port 4 with the slots |05, as shown in Fig. 6, into the space |40 at the right of the piston head I6 of the main valve 8, and from there through the slots ||1, the annular channel H6, the conduit 8 and the pipe 20 to the working end 1 of the power cylinder |24 whereby the piston |25 is moved to the left.

When the piston |25 in its left hand end position is to be reversed, the valve |0 is pushed to the left by means of the reciprocating tool of the work table as previously described in such a manner that it again comes into the position shown in Fig. l with the spring pressed ball I9 engaging the annular groove |4.

In this manner the annular space of the auxiliary valve |0 is connected through the slots |2, the annular channel H9, the passage |2|, and the pipe |23 with the discharge tank so that the pump delivers the working medium through the passage I, the annular space 44, the port 4, the annular space |40, the slots |1, the annular channel H6, the conduit 8, the annular space ||8 and the slots |49, into the annular space and from there' into the discharge.

Since at this instant the return end 99 of the power cylinder |24 is also in communication with the discharge tank as previously described, the power piston |25 remains stationary at the instant when with the aid ofthe piston 4| the working end 2| of the power cylinder 41 is connected with the discharge tank. The pres' sure medium no longer exerts any force on the main valve 8 so that it is pushed to the right by the spring |5. About the instant when the right hand edge of the piston |1 covers the port I8, the left hand edge of the piston begins to open the left hand inclined end surface |20 of the slots |05. The connection of the annular space 82 with the discharge tank is thus interrupted and the annular space 82, as the piston head I8 moves to the right under the action of the spring I5, is gradually connected with the delivery side of the pump through the passage l, the annular space |44, the port 4, the annular channel |04,

and the slots |05. The pressure in the annular space |39 rises and is transmitted through the slots ||0, the annular channel |09, the passage f' and the pipe ||5 to the return end of the power cylinder so that the piston |25 is reversed and now moves oppositely to its previous right hand movement.

If the machine is to be stopped the control valve 3, as shown in Fig. 6, is turned a certain amount and at the beginning of this movement is simultaneously pushed against the action of the spring |30. This lifts the pin |32 out of the notch |41 and the pin 32 slides under the influence of the spring |30 along the oblique surface |48 so that the valve 3 is shifted to the left and its head |28 covers the passage |45 and in this manner by means of the annular space |44 of the inlet passage the pump is directly connected with the channel |45 and hence with the discharge tank so that no power is exerted on the power piston |25.

Also the control device shown in the Figs. 8 to 15 is equipped with three slide valves, namely the main valve 18, by means of which the working cylinder is reversed, the control valve 19, which serves for engaging and disengaging the machine tool, as hereinafter described in connection with Fig. 15, and the auxiliary valve 80, which controls the main valve 18 and which can be moved by means of a stop-actuated control shaft. The drive of the auxiliary valve is known and is therefore not nearer described.

In the casing 8| of these valves three mutually parallel bores are formed, which are lines with bushes. In the bore 82 the main valve 18 is slidably arranged and the valves 19 and 80 are arranged in similar manner in the bores 83 and 84 respectively.

The main valve 18 is equipped with three piston heads 85, 88, 81; between which the body of the valve is reduced, so that annual chambers are formed. On the outwardly facing side of the piston head 85 the main valve 1B has an elongation in the form of a shaft 89. 9| denotes a spiral spring, the one end of which engages the outer end of the shaft 89, whilst the other end is seated on some member which is rapidly connected to the casing. The piston heads 85, 86, 81 are all of the same diameter, whilst the shaft like elongation 89 is of a somewhat reduced diameter. At the left end of the bore 82 a guide member 88 is arranged, which is pressed against the outer end of the bush 93 by means of a cover 92.

94 denotes the annual space between the piston heads 85 and 86, and 95 denotes the annulanspace between the piston heads 88 and 81. Between the outer side of the head 85 and the guide member 88 an annular space 96 is shown, the volume of which changes with the position of the main valve. The other side of the bore 82 is closed by a member 91 and a cover 2|. Between the outer side of the head 81 and the member 91 a hollow space is shown, the volume of which changes with the position of the valve'18.

In the control valve 19, which is located in the bore 83 and serves for engaging and disengaging the machine, an annular groove 23 is formed (Figs. 8 and 9), from which two short longitudinal grooves 24 extend. Perpendicularly to the grooves 24 also two longitudinal grooves 25 are formed which extend from the right hand end of the control valve to a point near the groove 23. Both ends of the bore 83 are closed by some4 suitable means. The valve 19 can be rotated and moved in the longitudinal direction by means of an outwardly projecting rod 39.

The auxiliary or reversing valve 80, which can 75 83 through slots 5|.

beV- moved in axial direction in the bore u, is

equipped with seven piston heads, 28, 21, 28, 28, 38, 3| and 32 of equal diameter, between which annular spaces 33, 34, 35, 38, 31 and 38 are formed. The left end of thebore 84 is closed by the piston head 25, and the right end by a cover 2|.

As it will be seen. particularly from Fig. 11, the pressure iiuid from the delivery side of the pressure fluid pump enters the casing 8| through an opening 48, which communicates with the three bores 82, 83 and 84 through a channel 4| in the casing 8|. 'Ihe bore 82 communicates with the channel 4| through slots 42 in the bush 83, and the bore' 83 communicates with the channel 4| through a bore in the bush 45 or through two bores 43 arranged diametrically opposite each other in the bush 45. Slots 44 in the bush 45 form aconnection between the channel 4| and the interior of the bore 84.

The system serves to control the oil supply of a hydraulically driven reciprocatory tool or element of a machine toolv indicated diagrammatically in Figs. 8, 13 and 14. In the example illustrated it is assumed that the machine is a shaping machine. On the machine frame is xed a power cylinder |58 in which a piston |5| is longitudinally slidable. The piston has a rod |54 connecting it rigidly to the ram |55 of the shaping machine, in which the `shaping tool is mounted in well known manner. The cylinder chamber at the right hand of the piston |5| is designated |52, and the chamber to the left of the piston is designated |53, the eiective piston area in this chamber being less than the piston area in chamber |52, by the cross-sectional area of the piston rod |54. The arrangement is such that when pressure medium operates in the chamber |52in which the piston area is greater, the ram is moved forwardly to effect its working stroke and make a cut with the tool. The cylinder chamber |53 is used for the return stroke of the ram |55. For` simplicity the chamber |52 is herein designated as the right or working chamber, and the chamber |53 as the left or return chamber. rThe return chamber |53 is connected through a conduit 41 ,with a channel 48 surrounding the bore 82, which channel communicates through ports 48 with the interior of the bores 82. The right-hand chamber. |52 is connected by a conduit 584 with a. port 5| which connects three bores 82, 83 and 84 with each other. In the region of the port 5|` the sleeve 45 of the bore 83 is provided with no slots while the port 5| is connected by slots 52 with the interior of the bore 82, and by slots 55 with the interior of the bore 84. The right-hand end of the interior of the bore 84 is also connected through a conduit 51 with the right-hand end of the bore 82, and through a passage 58 with a pipe |55 indicated in Figs. 813, 14 and 15 by a chain dotted line going to the tank, not shown. In the sleeves 83 and 45 are provided slots 53, 54 and 55 as shown, for the above mentioned purpose.

Between the encircling channels 4| and 5I a channel 58 is formed, which communicates with the bore 84 through slots 58 and with the bore In the same manner is on the left side of the channel 4| a channel 52 formed, which communicates with the bore' 84 through slots 53 and with the bore83 through A* slots 54.

Adjacent the outer left end of the bush 83 of the main control slide 18 a groove 55 is formed which surrounds the bores' 82, 83, 84 and communicates with the bores 82 and 84 through slots y58 and'51 respectively. In the bush 45 of the bore 88, however, no slots are formed in the vicinity of the channel 55. To the left hand side of the channel 55 also a channel 58 is formed, which interconnects the bores 82 and 84. In the guide member 88 radial slots 58 and longitudinal slots 18 are formed, through which the chamber 85 communicates with the channel 58. Slots 1| form a connection between the channel 58 and the boro 8 The right end oi' the bore 83 is connected through the bore |51 with the outlet container.

The annular space 35 of the auxiliary valve 88 communicates with the annular space 33 through the transverse bores 121 the longitudinal bore 13 and the transverse bores 14. The annular space -35 communicates with the annular space 38 through the transverse bores 15, the longitudinal bore 15 and the transverse bores 11. Y

The control deviceshown in the Figs. 8 to 12 inclusive operates in the following manner:

The return stroke side |53 of the working cylinder |58 having the smaller piston surface communicates with the conduit 41, and the forward stroke. side |52 of the working cylinder communicates with the conduit 58. In Figs. 8, 13 and 14 the central control valve 18 is shown in a position it will take up when the machine is running. The pressure iiuid from the pump enters the casing 8| of the control device .through the opening 48 and flows through the channel 4| and theslots 42 into the'annular space 85 of the main valve 18. The pressure iluid thereupon flows into' the cylinder, at the right side |52 ofthe same,

through the slots 52, the channel 5| and the conduit 58.

From the channel 5| the pressure uid also ows through the slots 55 into the annular space oi.' the auxiliary valve 88, from where it ows into the space 22 of the main valve 18 through the slots 54 and the channel 51. Thus, the valve 18 is securely held in its left, position against the pressure exerted by the pressure uid on the right side of the piston.

From the left side 53 of the cylinder |58, which in the described example corresponds with the return stroke of the machine, the pressure iluid flows through the conduit 41, the channel 55 and the slots 51 to the annular space 34 of the auxiliary valve 88. From the space 34 the pressure fluid ows through the slots 53, the channel 52 and the slots Y54, and leaves the device through the longitudinal grooves 25, bore 83 and bore |51.

The delivery side of the pressure uid pump also communicates with the annular space 35 of the auxiliary valve 88 through the channel 4| and the slots' 44. The pressure fluid thereupon l i'lows through the transverse bores 15, the longitudinal bore 15 and the transverse bores 11 to the annular space 38. From this space the pressure fluid ows through the slots 54 and the channel 51 into the space 22, from which it acts upon the head 81 of the valve 18.

31, the slots 58, the channel 58 and the slots 5|. 75

The piston head 32 of the auxiliary valve 80 also uncovers the slots and the channel 58 and conduit |56, whereby communication is established between the space 22 and the outlet container through the slots 53, the channel 51, the slots 55 and the annular space 38.

The spring 9| of the valve 18 is no longer opposed by any force and therefore moves the main valve to the right, hereby overcoming the frictional resistance. The spring is assisted in its action by the circumstance, that the annular space 35 of the valve 80, Fig. 13, now communicates with the slots 44 in the bush 46, Through this the delivery side of the pump is over the bores 12, 13 and 14 connected with the space 33, which at this moment is on the level of the slots 1|. The pressure fluid will therefore flow through these slots, the channel 68, the radial slots 69 and the longitudinal slots 10 into the annular space 96 and act upon the left side of the piston head 85.

The pressure fluid pump now communicates with the left side |53 of the power cylinder |50 through the channel 4|, the slots 42, the space 94, the slots 49 and the conduit 41. i.

When reversing from rearward stroke to forward stroke the auxiliary valve 80 is again moved into the position shown in Fig. 8. The pressure iluid flowing from the right side |52 of the cylinder |50 through the conduit 50 will accumulate in the channel 5| and the annular space 38, because the slots and the channel 59 are shut oil by the piston 3 I. The pressure of the accumulated fluid is transmitted through the slots 54, the channel 51 and the slots 53 to the space. 22 and the main valve 18 is moved to the left against the pressure of the spring 9| by the fluid pressure acting upon the right side of the piston 81.' This effect is augmented by the circumstance, that the space 22 as described communicates directly with the "delivery side of the pressure iiuid pump through the channel 4|, slot 44, annular channel 36, bores 15, 16, annular channel 3B, slot 54, channel 51, slot 53, and the bore 16.

The bushing 93 is provided with a conical annular groove 98 on the end lying left from the slots 66.

When the main valve 18 moves towards the left end from the position of Fig. 13 to the position of Fig. 8, this movement is gradually retarded as soon as the piston head 85 has covered the slots 66 because the uid in the chamber 96 can only escape through the conical annular groove 98 which gradually grows narrower in concert with the movement of the piston.

The middle slide valve 19, as shown in Fig. 14, may be moved suiciently to cause the annular space 23 to register with the slot 64. In this position the space 23 is connected through the short longitudinal grooves 24 with the ports 43 which are in communication with the delivery side of the pump for the pressure medium. In'this manner, as will be seen from Fig. 14, the pressure medium flowing out of the left-hand chamber |53 of the power cylinder, when the main valve 18 and the auxiliary valve 80 are in the position shown in Fig. 8, passes through the channel 65, the annular space 34, the channel 62, the slot 64, the annular space 23, and the longitudinal grooves 24, to the delivery side of the pump. On the other hand, when the middle slide valve 19 is in such a position, and the main slide valve 18 and the auxiliary slide valve 80 are in the position shown in Fig. 14, then the operation of the system according to this gure is not changed in any way.

The pump is now connected only to the port 40, the channel 4|, the ports 43, the annular space 23, the slot 64, the channel |52 and slot 63, in communication with the annular chamber 34 of the auxiliary slide valve 80, from which the pressure medium cannot escape and thus cannot exert any force on the auxiliary slide valve. Since this position can be readily understood from Figs. 13 and 14 it is not illustrated separately.

In Fig. 15 there is shown the manner in which the machine tool and the working cylinder |50 can be put out of operation. For this purpose the delivery' side of the pump is put in direct communication with the tank by turning the middle or control valve 19 through 90 as shown in Fig. 15. The delivery side of the pump is then connected through the port 40, the channel 4|, the ports 43, the longitudinal slots 25 in the valve 19, the bore 83 and the bore |51, to the tank, so that no force is exerted on the piston 5| of the working cylinder |50. This action is independent of the position of the main slide valve 18 and auxiliary valve 80. By turning the valve 19 through 90, the described direct connection of the pump to the tank is produced also in the case when the valve 19 is in the position shown in Fig. 14, prior to the said turning.

Fig. 16 is a 4flow sheet in which the various details correspond to the setting of the'members as in Fig. 13 except that the slide 19 is shown as moved entirely to the left for a clearer showing..

I claim as my invention:

1. A hydraulic control system for reciprocatory machine tools comprising a power cylinder for operating the machine part to be reciprocated, means for supplying hydraulic medium under pressure, a main valve cylinder, a spring held slide valve vtherein, having two pistons of different diameters of which the piston of larger diameter and the main valve cylinder form a chamber, means for connecting the chamber with the exhaust ,from the power cylinder, an auxiliary valve cylinder, a slide valve therein actuated by reversal of the machine part to be reciprocated, and a system of passages and ports for the hydraulic medium and means inter-connecting said power and valve cylinders with the pressure means so that in one position of the auxiliary valve one end of the power cylinder is connected to the pressure means by way of the main valve cylinder and the other end of the .power cylinder is connected to an exhaust by way of the auxiliary 4valve cylinder, and in another position oi' said auxiliary valve the second mentioned end Aof the power cylinder is closed until the therein entrapped medium operates the main valve through passages in said system against its spring, said main valve then connecting said second mentioned end of the power cylinder to the pressure means and its other end to the exhaust.

2. A system according to claim 1, in which the main valve having the two piston heads of different diameter form between themV an annular chamber in the main valve cylinder, and the spring of the main valve is so arranged that the pressure differential acting on said piston heads due to pressure medium in said chamberl is effective in the same direction as the spring.

3. A hydraulic control system for machine tools, comprising a power cylinder having a working piston reciprocable therein, means for supplying a pressure medium, a spring-actuated main valve slidab'le in a casing, a conduit connecting one end of said power cylinder to said main valve; an auxiliary-valveactuatedfby the reciprocation .of the working piston and inserted in said conduit, an exhaust portcontrolled by said auxiliary valve, pressure responsive means for operating the main valve against said spring,

said pressure responsive means being connected A to said conduit, a second conduit connecting the other end of the power cylinder tothe main valve,

pressure responsive means, consists of two valve heads of dlierent diameters in the main valve casing. A

5. A hydraulic control system for machine tools in accordance with claim 3, in which said pressure responsive means consists of two valve' heads of dierent diameters in the main `valve casing and the larger head forming a space with th adjacent end of the main valve casing connected with said mst-mentioned conduit.

6. A hydraulic control system for machine tools ln accordance with claim '3, in which said pressure responsive means consists of two valve heads of different diameters in the main valve casing andthe larger head forming a space with the adjacent end lof the main valve casing connected with' said first-mentioned conduit, and in which a manually operated control valve isv provided having a starting and a' stopping position and'being provided with a chamberconnected with said means i'or supplying pressure medium and an outlet port from said chamber.

whereby, upon setting the control valve to 11n-'- cover said outlet port permitting the pressure,

medium to pass out without s|ipplyingmediumy to the power cylinder, the vworking piston is stopped.

V1'?. A hydraulic control system for machineV tools, comprising a power cylinder having a reapressure medium, a set of valves arranged between .the power cylinder and said' means and comprising a spring actuated main valve slidable in a casing, a control valve having a run-l ning and stopping position and an auxiliary valve, means actuated by the power piston for automatically Vshifting the auxiliary valve at each end 'of the working piston stroke, said main valve having three heads of equaldiameters forming between them. two annularv spaces in the valve easing of constant volume and forming between 'the respective ends of the casing and each adiacent head a space of variable volume, said conl v trol valve being open to said annular spaces of the main valve, a conduit connecting oe end 'of said power cylinder with one of said variable spaces of the main valve, and `a. second conduit connecting the other end of said power cylinder with one of the annular spaces of constant volume, said auxiliary valve being inserted in both of s'aid conduits and having connection with an exhaust port and having also connection with said means ior supplying pressure medium; whereby the auxiliary valve'in one position closes -the connection between the exhaust port and said mst-mentioned conduit therebyY causing the pressure medium in the first-mentioned conduit to act against the headsof the main valve change its position.

narrawmnan'r. i

1o ciprocable Vpiston therein, means for: supplying 'y a 

